In a heavy saucepan set to medium heat, combine the milk and one cup of the heavy cream. Stirring frequently until the mixture reaches 170 degrees and bubbles begin to form around the edges.
While the milk mixture is heating, in a large bowl, whisk together the egg yolks, sugar and remaining 1/2 cup of heavy cream. Set aside.
Remove the milk from the heat and stir in cocoa powder and 4 ounces of the chopped Guittard chocolate, stir until the the chocolate is completely melted and mixture is smooth.
Slowly pour one cup of the hot milk mixture into the egg yolk mixture while whisking constantly. It may be helpful to set the bowl onto a kitchen towel to stabilize it while you whisk. Pour this mixture back into the saucepan and continue to stir over low heat until the temperature reaches 185 degrees F. The mixture should be slightly thickened, enough to coat the back of a spoon. Do not allow it to come to a boil.
Pour the custard through a fine mesh strainer into a clean bowl set over an ice bath to cool the mixture completely, stirring frequently to help the process along.
Once completely cooled, stir in vanilla extract and pour the custard into the bowl of your ice cream machine and churn for about 20 minutes or until set. Be sure to refer to the directions of your specific ice cream maker.
While the ice cream is churning, place the remaining 4 oz of chocolate in a microwavable bowl. Heat in 20 second intervals, stirring in between, until the chocolate is melted and smooth.
Once the ice cream is set, transfer 1/3rd of the frozen ice cream to an airtight container. Drop spoonful's of the marshmallow creme over the surface, drizzle some of the melted chocolate over the top and layer with the graham cracker pieces. Repeat the layers two times; ice cream, marshmallow creme, melted chocolate and graham crackers. Cover and freeze until solid, about 2 hours.